Continuous process of preparing fired ferrite cores



April 23, 1968 E. A. SCHWABE 3,378,896

CONTINUOUS PROCESS OF PREPARING FIRED FERRITE CORES Filed Nov. 16, 1964 4 Sheets-Sheet 1 g l/VVE/VT'OR v farm 4X04 Jeanna:

ATTORNE S.

April 23, 1968 E. A. SCHWABE 3,378,896

CONTINUOUS PROCESS OF PREPARING FIRED FERRITE CORES Filed Nov. 16, 1964 4 Sheets-Sheet 2 4g; 9 2 0 secs: 0 y a: l 1 w 59 i I 53 5 T Jig Z I 556 5a 57 i i I L ,4 I IT 4 III- FIG.3

//V VEN TOR. ffifewmafliwa me ATTORNEYS.

April 23, 1968 E. A. SCHWABE 3,373,896

CONTINUOUS PROCESS OF PREPARING FIRED FERRITE CORES Filed Nov. 16, 1964 4 Sheets-Sheet 5 Air Vacuum IN VEN TOR. Dar/W0 ,4 d aw/m;

W AQu W ATTORNEYS.

April 23, 1968 E. A. SCHWABE CONTINUOUS PROCESS OF PREPARING FIRED FERRITE CORES Filed Nov. 16, 1964 FIG.7

4 Sheets-Sheet 4 ATTORNEYS.

United States Patent 3,378,896 CONTINUOUS PROCESS OF PREPARING FIRED FERRITE CORES Eberhard A. Schwabe, 148 De Mott Lane,

New Brunswick, NJ. Filed Nov. 16, 1964, Ser. No. 458,801

(Filed under Rule 47(b) and 35 U.S.C. 118) 6 Claims. (Cl. 25-2) This invention relates to a rapid continuous method of preparing minute ferrite cores such as used for memory cores.

The trend in computers has been in the direction of the miniaturization of the computer units. In order to make smaller and smaller units, the demand for ferrite memory cores has been for those of extremely small dimensions. Whereas memory cores of toroidal shape with inside diameters (I.D.) of .050" and outside diameters (O.D.) of .080" are still used, these'are fairly large cores compared to those now specified which may have an ID. of .013 and CD. of .020 for example.

Contrary to the advances made toward miniaturization of the computer and its elements, no substantial advance has been made in the miniaturization of the apparatus for manufacturing ferrite memory cores. Although the kilns or furnaces employed in firing fenrites may not be as large and bulky as those for firing ceramic insulators, for example, such furnaces still have a high capacity for firing cores so that in order to operate such furnaces economically, millions of cores must be molded to shape beforehand and so as to be ready for feedingto said furnaces together. As a consequence, usually a substantial portion of the cores made from a particular new batch of ferrite composition have been molded and fired before the fired cores could be tested and often millions of cores produced this way have to be rejected due to an error in preparing the batch, firing or due to molding with the wrong pressure etc. Generally, the lapse of time between the time when a batch of cores is first prepared and the time when the fired cores of the batch can be tested is of the order of several days to as much as days.

Among the objects of the present invention is to produce a rapid firing process for ferrites so that it will be known within several minutes after a batch is put to use whether it produces satisfactory cores or not.

The molding of ferrites to form small cores of .020- .050" CD. or less is best done on more or less delicate molding machines of the type ordinarily employed for molding pills. Since many such small molding machines are ordinarily required to supply the load for one ordinary kiln it has not been considered practical to mount such molding equiment in the same room with the ordinary kilns for firing ferrites.

Among other objects of the present invention is to provide a combination molding and firing device for ferrites so that the molded ferrites pass directly from the molding machine to a continuous furnace in which they are completely fired and discharged ready for use.

Among still other objects of the invention is to provide an efiicient system for continuously molding ferrite material to shape, feeding the individual, shaped pieces as molded onto a continuously moving belt of a furnace and firing the monolayer of the shaped ferrite bodies.

Since the cores are fed to the furnace conveyor one by one and come off the discharge end of the belt conveyor of the furnace, they may be fed directly to a core testing device without requiring any special conveyor means other than a chute.

The objects of the invention are attained by providing a miniature furnace which includes a continuously moving refractory belt feeding means of a width to accommodate one or several of the largest diameter cores to be "ice made when placed flatly thereon, providing one or several core molding devices with their mold cavities at a level somewhat above the refractory belt of the furnace and providing a chute extending from the molds of the core molding devices to a portion of the continuous belt which extends outside of the furnace.

If desired, a chute can be provided at the discharge end of the refractory belt to guide the fired cores directly to a core testing machine. Since the cores are arranged in a monolayer on the belt, no additional aligning means is required to feed the cores one at a time to the tester.

The molding devices are of conventional type with conventional ejecting means for the molded body. If desired, a suction means or air blast may be added to direct the molded core into the chute.

The furnace is of the order of one or two feet in length and has a muffle tube extending therethrough, through which a refractory belt is passed. Means are provided to feed air and nitrogen to certain zones of the mufile and to withdraw a mixture of air and nitrogen from another zone thereof. The furnace is preferably electrically heated. In the production of ferrite memory cores, the firing itself may be critical and the quality of the finished core depends in no small part on the firing cycle. According to this invention a miniature, fast firing mnfile has been found to be atmospherically controllable to provide fired ferrite memory cores of uniform, high quality.

An inert gas at about room temperature such as nitrogen is introduced into the kiln at the exit end thereof to prevent reoxidation of the product before leaving the kiln. In place of nitrogen, argon, carbon dioxide, water vapor and similar inert gases or gas mixtures may be employed.

Other features and advantages of the invention will be made apparent from the following detailed description of a specific form thereof, when read in connection with the accompanying drawings in which:

FIG. 1 is a top plan view of the chute guide and furnace portion of the apparatus of the invention.

FIG. 2 is a side view, somewhat diagrammatic, of the combination molding device, kiln or furnace and testing device.

FIG. 3 is an end view of the apparatus of FIG. 1 with the drive wheel removed.

FIG. 4 is a side cross-sectional view of the kiln.

FIG. 5 is a horizontal cross-sectional view taken through the muffle tube of the kiln or furnace.

FIG. 6 is a partly diagrammatic view showing the path of a core through the combination apparatus and including the testing device.

FIG. 7 is a side view of the chute, kiln or furnace and the belt conveyor means for the latter.

FIG. 8 is a detail cross-sectional view of the chute.

As illustrated in FIG. 2, the entire continuous apparatus comprises the molding device 10, the chute 20, the conveyor belt 30 and furnace or kiln 40, a second chute and testing means 80.

The molding device 10 may be any conventional molding device. With different devices, the position of the jet means 11 (see FIG. 1), for propelling the molded core into the chute 20 may have to be adjusted and the chute supporting means 12 (see FIG. 7) may have to be changed. The supporting means 11 was provided for a stokes press of the type often used for the manufacture of pharmaceutical pills. The die employed in the press is one for forming a toroidal core 91 with an outside diameter of .020 to 0.050" and an inside diameter of .013 to .030".

As the molded ferrite core body is being ejected from the molding press it is moved into the path of the blast of air from the jet 13 of jet means 11 and is propelled into the funnel shaped mouth 21 of chute 20. Once in the chute 20, the core 91 passed down the enclosed side channel 22, into the opening 23 at the end thereof through the opening in block 24, tube 25 and exit block 26, where it is fed onto conveyor belt 30. A space adjuster means 27 is provided at the exit end of the exit block 26 to prevent any upright core from passing on into the furnace and causing such upright cores to fall fiat on the belt 30.

The conveyor belt 30 is a continuous iicxible belt of refractory material. A #80 mesh belt made of a platinum- 10% rhodium alloy has proved to be very satisfactory. One advantage of the miniature, high speed, kiln is that the best materials can be employed for the construction of certain parts such as the conveyor belt 39. With conveyor means made of ceramic products or base metals there is always the danger of contamination of the product being fired, through an exchange reaction for example, between the materials being fired and the ceramic supporting means at the high temperatures required for firing. The metals and alloys of the platinum group are among the most inert materials available for supporting molded ferrite bodies during firing and although their cost would be practically prohibitive with kilns and furnaces of conventional size, they are economical for the present apparatus.

The belt 30 is supported and driven by the spaced wheels 31 and 32. The wheel 32 is driven by motor 33 which is connected to speed reduce-r 34. Wheel 31 is also driven from the motor 33 through coupling 35, shaft 36 and speed reducer 37 (see FIG. 1).

The wheels 31 and 32, the furnace 4t) and the lower end of chute 20 are supported from the platform 38. The furnace or kiln 40 is adjustably supported above the level of the platform 38 by means of screw shafts, nuts 42, 43 and thermal insulators 44. The kiln or furnace itself com prises the mufiie tube 45 of high temperature alumina or equivalent material (see FIG. 4). The intermediate portions of tube 45 are supported between fire bricks 46 (below) and 46' (above) which in turn are supported by the support means 47 formed of a temperature resistant material like Transite. The brick supports 47 are preferably formed in one piece adapted to completely surround bricks 46 and 46' and said supports 47 fit into the metal casing 48. The regions between bricks 46, 46, supports 47 and the casing 48 are filled with mineral wool or similar insulating material. As shown in FIG. 4, the ends of the fire bricks 46, 46 support the tube 45, but said bricks have a hollow channel 49, 49' intermediate the ends. Electrical resistance heating coil 50 is wrapped around tube 45 within the channel portions 49, 45" of bricks 46, 46'. A suitable material for the heating coil wire is 90 Pt/lO Rh alloy. The coil 50 may be coated with refractory cement 52. The leads (not shown) for coil 50 are brought out between the bricks 46 and 46. The re sistance wire 50 is adapted to heat the mufiie tube to temperatures up to 1500" C.

The entrance end of the furnace or kiln (which is shown at the right-hand side of FIGS. 1, 2, 4 and 5) comprises an insulating plate 53 and a cover plate 54. The end of muffle tube 45 extends through the opening in insulating plate 53 and partly into cover plate 54, but the outer side of cover plate 54 is substantially closed but contains the conveyor belt 30. The exit end 56 of kiln 40 comprises the insulating plate 57 and the cover plate 58. As shown in dotted lines, in FIG. 4, the tube 45 extends through insulating plate 57 but only a short distance into the chamber 59 formed between cover plate 58 and end plate 59. Cover plate 58 also contains a slot 60 for the passage of the conveyor belt 30. Cover plate 58 also contains a hose fitting 61 connecting to chamber 59 through which nitrogen or similar gas may be introduced into tube 45. As shown in FIG. 3, the cover plate 58 contains two cylindrical openings 62 and 63 positioned below the slit 60 but adapted to open into the tube 45.

Tubes 64 and 65 extend through and substantially fill the openings 62 and 63. Tube 64 is closed at the inner end 66 but contains an opening 67 near the end thereof which as shown in FIG. 5 is approximately at the entrance end of the mufiie tube 45. Tube 65 is closed at the end 68 but includes an opening 69 at approximately the central portion of the tube. An additional smaller opening may be provided in one or both of end plates 54 or 58 for admitting a thermocouple. As shown in FIG. 1, the open end of tube 64 is connected to air supply hose '79 and the open end of tube 65 is connected to a vacuum hose 71. The hose connection 61 is connected to nitrogen supply hose 72. Introducing nitrogen at the exit end of the kiln prevents reoxidation of the fired cores.

As illustrated in FIGS. 2 and 6, the cores 91 arrive one at a time at the discharge end of belt 30 and can, therefore, be fed directly to a testing device 80. Any suitable testing device may be employed. In FIGS. 2 and 6, a tester similar to that of US. Patent No. 3,060,376 is shown diagrammatically. This tester requires that the core be delivered to the testing portion with its axis in a horizontal position. The chute 90 may have its aligning groove 92 spiraled so as to cause the core to move to an upright position with its axis horizontal as it is moved by gravity through the chute as illustrated in FIG. 6. No mounting is shown for testing device in FIG. 2, but it is preferably mounted separately so as to be free of vibrations produced by the molding press 10 which otherwise interferes with the testing.

In operation, a core is molded from ferrite powder mix at mold 10, as it is ejected from the mold it is propelled by a blast of air or drawn by a vacuum into chute 20, the chute 2t) deposits the cores as a monolayer onto belt 30. Belt 30 continuously moves through kiln or furnace 40. In the furnace 40, air is introduced at 67, to burn out the binder, nitrogen is introduced at the exit end through hose connection 61 and chamber 59 and both air and nitrogen are rapidly evacuated through opening 69 of vacuum tube 65 at an intermediate point within the mufile tube 45. The speed of belt 30 is adjustable so that the cores pass through the entire firing cycle in about 2 to 5 minutes. Close to the innermost region of the nitrogen portion of mufiie tube 45, the temperature of up to 1500 C. is registered, providing for fast firing of the ferrite. The cores are tested within a matter of a few minutes after being molded. If anything is wrong with the molded composition or the molding operation itself, it is discovered within a few minutes at the most, after a new batch is pressed.

The features and principles underlying the invention described above in connection with specific exemplifications will suggest to those skilled in the art many other modifications thereof. It is accordingly desired that the appended claims shall not be limited to any specific feature or details thereof.

I claim:

1. A process of manufacturing fired ferrite bodies comprising providing a ferrite forming powder containing the components of the desired ferrite and a binding agent, molding the powder to shape,

discharging the molded body from the mold and guiding it directly onto a moving refractory conveyor means in a single layer,

moving said ferrite body through a firing kiln by means of said conveyor,

burning out the binder in the presence of air and rapidly firing the ferrite body including passing said body through a zone at a temperature of about 1500 C. in an atmosphere of nitrogen,

adjusting the speed of travel through the kiln so that cores are delivered for testing in the course of about 2 to 5 minutes after molding, introducing inert gas into the kiln at the exit end thereof whereby the fired ferrite cores are protected from reoxidation.

2. An apparatus for continuously producing miniature fired ferrite bodies comprising in combination a molding device, a continuous miniature kiln comprising a firing zone and means to heat the kiln to the ceramic firing temperature of said ferrite and a continuously moving conveyor passing therethrough and extending beyond both ends of said kiln, delivery means extending from said molding device to the conveyor belt at a position outside the kiln and near the entry end of the kiln, means for transferring the molded body from the molding device to said delivery means, a supply of non-combustion sup porting gas, means for directing said non-combustion supporting gas to said firing zone to form an atmosphere thereof in said zone and removal means for delivering the fired ferrite from said conveyor for testing.

3. The apparatus of claim 2 wherein said kiln is of small size and including means driving said conveyor to convey ferrite bodies through the kiln at a fast rate providing a residence time between two and five minutes within the kiln.

4. The apparatus of claim 2 including a testing device for receiving fired ferrite from said removal means and testing the properties of the fired ferrite.

5. The apparatus of claim 2 including means for introducing combustion supporting gas into the entry end of the kiln.

6. The apparatus of claim 2 wherein said conveyor is a conveyor belt passing through the kiln and the belt is of a width larger than the largest dimension of the ferrite body and having substantial portions thereof extending beyond the ends of the kiln.

References Cited UNITED STATES PATENTS 1,864,769 6/1932 Sidell 18-1 X 1,891,469 12/1932 Coleman 25-142 2,530,595 11/1950 Blaha.

2,583,842 1/1952 Hendrickson 264-56 X 2,600,306 6/1952 Lipscomb 25-142 2,641,044 6/1953 Bearer 264-67 X 3,183,573 5/1965 Alexander 25-142 3,265,779 8/1966 Gobla et al. N 18-1 X 1,071,663 8/1913 Burley et a1. 25-144 1,708,124 4/1929 Dedouch 25-142 1,858,499 5/1932 Hathaway et al. 25-142 X 1,910,433 5/1933 Hathaway 25-142 2,052,324- 8/1936 Thomson 25-142 WILLIAM J. STEPHENSON, Primary Examiner. 

1. A PROCESS OF MANUFACTURING FIRED FERRITE BODIES COMPRISING PROVIDING A FERRITE FORMING POWDER CONTAINING THE COMPONENTS OF THE DESIRED FERRITE AND A BINDING AGENT, MOLDING THE POWDER TO SHAPE, DISCHARGING THE MOLDED BODY FROM THE MOLD AND GUIDING IT DIRECTLY ONTO A MOVING REFRACTORY CONVEYOR MEANS IN A SINGLE LAYER, MOVING SAID FERRITE BODY THROUGH A FIRING KILN BY MEANS OF SAID CONVEYOR, BURNING OUT THE BINDER IN THE PRESENCE OF AIR AND RAPIDLY FIRING THE FERRITE BODY INCLUDING PASSING SAID BODY THROUGH A ZONE AT A TEMPERATURE OF ABOUT 1500*C. IN AN ATMOSPHERE OF NITROGEN, ADJUSTING THE SPEED OF TRAVEL THROUGH THE KILN SO THAT CORES AS DELIVERED FOR TESTING IN THE COURSE OF ABOUT 2 TO 5 MINUTES AFTER MOLDING, INTRODUCING INERT GAS INTO THE KILN AT THE EXIT END THEREOF WHEREBY THE FIRED FERRITE CORES ARE PROTECTED FROM REOXIDATION. 